1.13.2 offline launcher issues

I have 4 computers set up with 1.13.2 on a home vanilla server, each using the Skaiacraft launcher, latest release. Each machine uses the same configuration, with the only difference being the player and profile.

2 play fine and 2 do not. Error message is something like “unable to load class.main something something”. These were able to play problem-free on 1.12.2.

If I connect the problem machines to the internet, launch the game, then switch to the LAN server, they play great.

I noticed tonight that on the launcher window, the functioning machines say “ready to play Minecraft 1.13.2” and the non-functioning machines both say “ready to update and play Minecraft 1.13.2” despite having the exact same build.

Specs are Windows 7, 64bit on 3 machines and Win10 64bit on the fourth. The Win10 machine is one of the problematic systems.

If I’ve left anything out, remind me and I’ll add it. Thanks for your time, and any insight you can provide.